Wednesday, June 17, 2009

Nature’s Delicate Tightrope Walk

We still have not fully understood the intricacies of working of nature. We fiddle with it sometimes with good intentions but end up getting counterproductive results. Here is an example of how overzealous conservation efforts drove a species of butterfly, Large Blue Butterflies’ (Maculinea arion), to extinction in UK but was brought back from the brink after careful study and understanding of the ecosystem processes. The whole scenario was the culmination of 40-year research effort by Dr Jeremy Thomas of the University of Oxford in Oxford, UK.

The butterflies disappeared from Britain in 1979. Butterfly collectors were generally blamed for the decline of this butterfly. This was far from the truth. The study throws light on how the large blue butterflies’ dependence on a single species of ant led to the butterflies' disappearance.

Adult females of Large Blue butterflies lay their eggs on Thyme flowers in the summer. The caterpillars secrete chemicals that attract red ants and fool them into thinking the caterpillars are ant grubs. The ants carry the caterpillars into their underground nests. Caterpillars that have been taken to the nest of one particular ant species, Myrmica sabuleti, will survive to adulthood. The caterpillars' secretions are a close match to those of M. sabuleti grubs. Ants never discover that they have been fooled, and continue to protect the caterpillars for 10 months even though they feed on the ants' own brood. In early June, the caterpillars form a chrysalis and crawl above ground. Two weeks later they become full-fledged butterflies.

In their overzealous attitude to conservation the authorities initially fenced off the habitat of the butterflies to prevent entry and give total protection to the butterflies. The scientists soon realized that the grass in the butterflies' habitat had grown too long, as grazing had been completely stopped with the formation of fences. The soil characteristics also changed. It was now too cool to support adequate numbers of M. sabuleti ants. Without enough ants to raise their young, the large blue butterflies dwindled.

In the late 1970s, after 40 years of trying to save the large blue by preventing entry of butterfly collectors, conservationists followed Dr Thomas' recommendations, They restored the butterfly' habitat by clearing scrub and reintroducing grazing animals. Grazing was intimately associated with the ecological processes.

Starting in 1983, Thomas and his colleagues began introducing large blue butterflies imported from Sweden, into the restored habitat. The butterflies started establishing. The butterflies now occupy 30 percent more colonies than they had in the 1950s. The large blue is now one of three butterflies on course to meet the Convention of Biological Diversity's target to reverse species' declines by 2010. In the 1970s, the International Union for Conservation of Nature selected three butterflies, the Large Blue, Queen Alexandra's Birdwing of Papua New Guinea and the monarch butterfly of North America as global flagships for the cause of lepidopteran conservation.

The research paper is entitled, "Successful Conservation of a Threatened Maculinea Butterfly." It is slated to appear in Science, at the Science Express website, on 18 June 2009.